Trilayer microlithographic process using a silicon-based resist as the middle layer

Abstract

A method for patterning an integrated circuit workpiece (10) includes forming a first layer (16) of organic material on the workpiece surface to a depth sufficient to allow a substantially planar outer surface (36) thereof. A second, polysilane-based resist layer (22) is spin-deposited on the first layer (16). A third resolution layer (24) is deposited on the second layer (22). The resolution layer (24) is selectively exposed and developed using standard techniques. The pattern in the resolution layer (24) is transferred to the polysilane layer (22) by either using exposure to deep ultraviolet or by a fluorine-base RIE etch. This is followed by an oxygen-based RIE etch to transfer the pattern to the surface (18) of the workpiece (10).

What is claimed is: 
     
       1. A process for applying a pattern to a workpiece used in fabricating an integrated circuit, comprising the steps of: depositing a thick organic layer on a surface of the workpiece;   depositing a second layer containing an at least partially silicon-based polymer on the thick organic layer;   depositing an organic photoresist resolution layer on the second layer;   projecting a pattern image onto the resolution layer with a light source to which the resolution layer is sensitive;   developing the resolution layer to leave patterned orifices therethrough and to expose patterned areas of the outer surface of the second layer;   exposing the resolution layer and the patterned areas of the second layer to light to which the second layer is sensitive but which will be strongly absorbed by the resolution layer;   developing the second layer to create orifices therein extending from the patterned areas of the outer surface of the second layer to corresponding patterned areas on the outer surface of the thick organic layer; and   differentially etching exposed portions of the thick organic layer much faster than the second layer until the surface of the workpiece is reached.   
     
     
       2. The process of claim 1, wherein said step of depositing a thick organic layer comprises the step of depositing a layer of Novolak photoresist. 
     
     
       3. The process of claim 1, and further comprising the step of depositing the thick organic layer to a depth in the range from about 1 to about 3 microns. 
     
     
       4. The process of claim 1, wherein said silicon-based polymer is selected from the group consisting of polysilanes, polysiloxanes, organosilicon compounds, and mixtures thereof. 
     
     
       5. The process of claim 1, and further comprising the step of absorbing wavelengths of light less than or equal to 340 nm by the second layer. 
     
     
       6. The process of claim 5, wherein said step of exposing the organic photoresist layer and the patterned areas of the second layer comprises the step of exposing the resolution layer and the patterned areas of the second layer to deep ultraviolet light having a wavelength less than or equal to about 248 nm. 
     
     
       7. The process of claim 1, and further comprising the step of depositing the second layer to a depth in the range of about 0.2 microns to about 0.5 microns. 
     
     
       8. The process of claim 1, wherein the resolution layer comprises Novolak photoresist. 
     
     
       9. The process of claim 1, and further comprising the step of absorbing wavelengths of light less than or equal to 248 nm by the resolution layer during said step of exposing the organic photoresist layer and the patterned areas of the second layer. 
     
     
       10. The process of claim 1, and further comprising the step of depositing the resolution layer to a thickness of about 0.9 microns. 
     
     
       11. The process of claim 1, wherein said step of differentially etching comprises the step of etching the exposed portions of the thick organic layer with a reactive ion etch that attacks the thick organic layer at a much faster rate than the second layer. 
     
     
       12. The process of claim 11, and further comprising the step of creating a plasma etchant from a gas selected from the group consisting of oxygen, hydrogen and nitrous oxide. 
     
     
       13. The process of claim 12, wherein said gas comprises oxygen.